1. Field of the Invention
The present invention relates generally to functionally graded friction material, and more particularly to a functionally graded friction material containing a fiber reinforced composite with heat conducting elements therein that offers better wear resistance due to frictional and thermal conductivity properties. The improved friction material is particularly suited for use as a facing material in clutch or brake applications.
2. Description of the Related Art
Friction material is currently used in many industrial applications, for example, in vehicle clutches, brakes, synchronizers in transmissions, clutch packs in limited slip or locking differentials, industrial or marine couplings, as well as in a variety of other applications. Desirable characteristics of a good friction material include low costs, high wear resistance, high heat resistance, high coefficiency of friction as well as consistence of coefficiency of friction over a wide heat and load range, and time periods. In a friction device, there is typically at least two cooperating members with at least one of the cooperating members being a support member and having a friction material surface that is constructed to be moved into and out of engagement with the opposing surface on the other cooperating member. Some applications of these devices are usually referred to by their particular purpose, for example, a dry brake or clutch which as used herein is intended to mean a brake or a clutch wherein the friction surfaces are dry. In contrast, a wet brake or clutch is intended to mean a brake or clutch wherein the friction surfaces are lubricated, or are cooled by direct or indirect contact with a liquid. The friction material of the present invention is applicable to either application.
Commercially available friction materials include pyrolytic-carbon fabric material as disclosed in U.S. Pat. Nos. 4,700,823; 4,844,218; and 5,858,511 which are all assigned to the Assignee of the present invention, and hereby incorporated by reference. Fiber reinforced polymer composites are commercially available and may be manufactured in a variety of ways including those described in U.S. Pat. No. 5,646,076.
Still, there exists a need for an improved friction material and methods for making the same. The improved friction material should offer better wear resistance and longer useful life by exhibiting improved frictional and thermal conductivity properties.